(S)-(−)-1-(4-Fluoroisoquinolin-5-yl)sulfonyl-2-methyl-1,4-diazepane is a compound represented by the following formula (1):

and particularly, the hydrochloride dihydrate of the above compound is a non-hygroscopic, water-soluble crystal with excellent chemical stability, for which it is known to be useful as a pharmaceutical product (see Patent Documents 1 and 2). These isoquinoline-5-sulfonamide compounds are known to be useful as preventive and therapeutic agents for cerebrovascular disorders such as cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage, and cerebral edema, particularly as preventive and therapeutic agents for glaucoma (see Patent Documents 1 to 5).
Conventionally, as the production method for the aforementioned compound, for example, a production method performed by the method described in Patent Document 1, which is illustrated by the following production process, is reported (Production method 1-A).

That is, it is a method for producing the desired compound (1) by synthesizing a compound (4) by reacting (S)-1-tert-butoxycarbonyl-3-methyl-1,4-diazepane (3) with 5-chlorosulfonyl-4-fluoroisoquinoline (2) in methylene chloride in the presence of triethylamine (Step 1), and then deprotecting the compound (4) thus obtained by adding trifluoroacetic acid in methylene chloride (Step 2).
Also, it is known that (S)-1-tert-butoxycarbonyl-3-methyl-1,4-diazepane (3), which is an important intermediate for the production of the aforementioned compound (1), can be produced by, for example, a method such as those shown below (production method 1-B; see Patent Document 1).

Also, meanwhile, it is known that the compound (1) can also be produced by a production pathway such as those shown below (production method 2) (see Patent Document 1).
